Inhibitions of ACh (0.1-3.2 ug/ml)-induced contractions of the guinea pig isolated ileum probably indicate possession of antidiarrheal activity of APE. The exact mechanisms of APE action on the smooth muscles could not be established in the present study.
INTRODUCTION
AIMS AND OBJECTIVES
- OBJECTIVES
The aim of this study was to investigate the pharmacological effects of Hypoxis hemerocallidea Fisch. The objectives of the study were to examine the pharmacological effects of Hypoxis hemerocallidea on the following extravascular smooth muscle in vitro. a) to examine the uterolytic effects of APE on isolated spontaneously contracting uterine horns in non-pregnant rats; as well as in acetylcholine and potassium chloride isolated uterine horn contractions from stilboesterol-prone, estrogen-dominant non-pregnant rats;.
SMOOTH MUSCLE PHYSIOLOGY
FUNCTIONS OF SMOOTH MUSCLE
The extensive layers of smooth muscle in the walls of the digestive tract play an essential role in moving materials through the tract. Smooth muscles in the walls of the gallbladder contract to expel bile into the digestive tract.
SMOOTH MUSCLE STRUCTURE, INNERVATION AND STIMULATION
Multiunit smooth muscle cells resemble skeletal muscle fibers and cardiac muscle cells in that nerve activity produces an action potential that propagates over the sarcolemma. The structural organization of single-unit and multi-unit smooth muscle cells is shown in Fig.3.
LENGTH-TENSION RELATIONSHIPS IN SMOOTH MUSCLE CELLS
SMOTH MUSCLE CONTRACTION
- Examples of the types of smooth muscle contraction
Phosphorylation of MLC leads to cross-bridge formation between myosin heads and actin filaments, and thus, smooth muscle contraction. The different rates of Ca influx and efflux make it possible for there to be moment-to-moment net gains and losses of calcium available to initiate a contraction, in smooth muscle cells (Johnson, 2003). Contraction is initiated by an increase in Ca2+ in the myoplasm (file://E:\SMOOTH MUSCLE.htm).
The state of light chain phosphorylation is said to be further regulated by MLC phosphatase, which removes high-energy phosphate from the light chain of myosin to promote smooth muscle relaxation. Regardless of the stimulus, smooth muscle cells use cross-bridge cycling between actin and myosin to develop force, and calcium ions serve to do so. The binding of an agonist (e.g. norepinephrine or oxytocin) to the surface receptor of a smooth muscle induces a signal that spreads from the outside to the inside of the plasma membrane, activating several effectors that ultimately initiate contraction (file:/ /E: \GLAD MUSCLE.htm).
SMOOTH MUSCLE RELAXATION
- Vascular relaxation mechanisms
Inhibition of the receptor- and voltage-gated calcium channels located in the plasma membrane can lead to relaxation of smooth muscle. This is because these channels are important for calcium influx and smooth muscle contraction. These include benzodiazepines and dihydropyridine; which binds to various receptors on the channel protein and inhibits calcium entry into smooth muscle.
Smooth muscle relaxation occurs either as a result of removal of the contractile stimulus or by the direct action of a substance that stimulates inhibition of the contractile mechanism. According to Benoit et al. 1997), in vitro studies show that phosphorylation of myosin kinase via a cAM-dependent pathway decreases the affinity of the myosin kinase for the calcium-clamodurin kinase responsible for the phosphorylation of myosin. is a decreased sensitivity of the smooth muscle contractile machinery. As stated by Benoit et al. i) the cGMP-dependent kinases suppress the rise in cytosolic calcium that occurs in response to vasoconstrictor agonists such as angiogenesis II. ii) the effect of cGMP on smooth muscle is via calcium ATPase activity and can be increased by cGMP-dependent protein kinases.
PLANT MATERIALS
The experimental protocols and procedures used in this study were approved by the Animal Ethics Committee of the University of KwaZulu-Natal, Durban 4000, South Africa; and in accordance with the "Guide for the Care and Use of Laboratory Animals in Research and Teaching" [published by the Ethics Committee of the University of KwaZulu-Natal, Durban 4000, South Africa]. Under reduced pressure in a rotary evaporator (see Figure 6) at a temperature of 55±1 °C, the supernatant was concentrated to dryness in small amounts at a time. These were then lightly ground to obtain a crystalline powder of 'African potato' aqueous extract (APE).
Aliquots of the extract were weighed without further purification and dissolved in distilled water (at room temperature) on each day of my experiments.
ANIMAL MATERIAL: TISSUE PREPARATION AND METHODOLOGY
- ISOLATED UTERINE HORNS
- RAT ISOLATED VAS DEFERENS
- GUINEA-PIG ISOLATED TRACHEAL SMOOTH MUSCLE
- GASTROINTESTINAL TRACT SMOOTH MUSCLE
The uterolytic effects of graded concentrations of APE (25-400 mg/ml) were studied on naïve female rat uterine horns in the absence and presence of some agonistic drugs. The uterolysic effects of APE (25-400 mg/ml) on uterine horns from stilboesterol-primed female rats were also examined in the absence and presence of some agonist drugs. Effects of graded concentrations of APE (25-400 mg/ml) were studied on rat isolated vasa deferentia in the absence and presence of some agonist drugs.
The broncholytic effects of graded concentrations of APE (25–400 mg/ml) were investigated in tracheal smooth muscle preparations isolated from guinea pigs in the absence and presence of drugs such as aminophylline, nitroprusside, and isoprenaline. The effects of APE (25-400 mg/ml) were examined in isolated guinea pig ileal tissues in the absence and presence of several agonist drugs. The lower concentration of APE was then added to the tissue and left in contact for 3 min.
DATA ANALYSIS
Each added APE concentration was left in contact with the tissue until a maximum relaxation effect was observed and then washed out with a physiological solution (5 to 6 times). After achieving a graded concentration-response effect to ACh alone, the tissue was allowed to rest for approximately 3 minutes. The concentration-response effect to the agonist, the same as previously performed in the same tissue, was then repeated in the presence of increasing concentrations of APE.
The time period between each addition of APE followed by the agonist was 3 min (APE was left in contact with the tissue for 3 min before adding the respective concentrations of agonist). The tissue was left to rest for 10-30 minutes after washing before the next concentration-response effect was determined.
Reproductive Smooth Muscles
- THE UTERUS
The lowest concentration of APE (25 mg/ml) produced the highest percentage of contractile amplitude, while the highest concentration (400 mg/ml) completely inhibited the uterine contractions. The initial increase in tissue contractile amplitude induced by ACh was inhibited by addition of APE; when APE was left in contact with the tissue for a period of 3 minutes, (see Fig.8). Comparative contractile effects of APE on isolated uterine horns from a non-pregnant rat, in the absence and in the presence of ACh.
Spasmogen-induced tensions developed by uterine smooth muscle were antagonized by increasing concentrations of APE. Tissue relaxations induced by additions of increasing concentrations of APE (100, 200, and 400 mg/ml) were concentration-related (see Figures 9 and 10). A representative trace showing the relaxant effects of APE (50, 100, and 200 mg/ml, respectively) added cumulatively to the bath fluid, to the right of 1, 2, and 3 downward-pointing solid arrows.
Potassium chloride + APE Control
APE Concentration (mg/ml)
THE VAS DEFERENS
Vas deferens smooth muscle contraction is usually associated with stimulation of alpha-adrenergic receptors, and relaxation is associated with stimulation of beta-adrenergic receptors. Adrenaline was used in this study to contract the smooth muscle of the vas deferens before the addition of APE (Walland et al; 1997). Adrenaline (0.2-1.6 ug/ml) produced concentration-related contractions of smooth muscle in the vas deferens of rats and guinea pigs.
Addition of APE (25-400 mg/ml) relaxed the muscles and antagonized the adrenaline-induced contractions of the tissues. The observed effects of increasing concentrations of adrenaline, alone and in the presence of the APE, are shown in Figure 11. Effects of increasing concentrations of adrenaline, alone (panel A) and in the presence of APE (panel B), on adrenaline-induced contractions of isolated vas deferens of a guinea pig.
Concentration
Respiratory Smooth Muscle
-receptor interactions regulate airway smooth muscle tone through activation of guanine nucleotide-binding proteins (G proteins), which are coupled to second messenger pathways that mediate changes in the contractile state of the tissue. Both the mobilization of calcium and the activation of PKC play crucial roles in the initiation and acute modulation of the intensity and duration of airway smooth muscle contraction. Bronchodilator agonist-mediated receptor activation is typically coupled to an increased accumulation of the second messenger, adenosine 3', 5', -cyclic monophosphate (cAMP), which, through activation of cAMP-dependent protein kinase, induces phosphorylation of specific proteins, leading to relaxation of smooth airways.
Calcium sensitization through this pathway is thought to play a role in the sustained phase of airway smooth muscle contraction, including human airway smooth muscle. The exact mechanism of the bronchospasmolytic action APE in this regard is not known; but is probably due to stimulation of the beta2-adrenoreceptors abundant in the bronchial smooth muscle. In the same study, it was also observed that APE inhibits the spasmogenic action of potassium on the tracheal smooth muscle preparations.
Gastro Intestinal Tract Smooth Muscle
Tissue contractions were induced by successive additions of increasing concentrations of ACh (0.1–3.2 μg/ml, respectively) to the bath fluid at bright points 1–6 (panel A). APE (25-400 mg/ml) antagonized ACh- and other spasmogen-induced contractions of the guinea pig ileum in a concentration-related manner. The results obtained in the present study support some of the folkloric claims about the therapeutic effects of "African potato".
However, overall, the exact mechanisms of action of the plant extract on the smooth muscle examined had not been established. Effects of Hypoxis hemerocallidea (Fisch.. amp; C. A. Mey) [Hypoxidaceae] tuber ('African Potato') aqueous extract on renal electrolyte and fluid handling in the rat. Evaluation of the analgesic, anti-inflammatory and antidiabetic properties of Sclerocarya birrea (A. Rich) Hochst.
InterScience'
Some of the non-pregnant (normal) rats and guinea pigs were pretreated with stilboesterol (0.2 mg/kg s.c.) 20-24 hours before use. In all cases, each of the graded concentrations of APE had occurred after maximum relaxation. Relatively low to high concentrations of APE (25-400 mg/ml) inhibited the amplitude and sometimes the frequency of the spontaneous, rhythmic contractions and relaxed the uterine muscle preparations in a concentration-related manner.
Relatively low to high concentrations of APE (25-400 mg/ml) consistently released basal tones of horn muscle preparations in a concentration-dependent manner. However, the results of this study indicate that APE has uterolytic activity in the mammalian experimental animals used. However, the spasmolytic effects of APE on spasmogen-induced contractions of uterine horn muscle strips taken from non-pregnant rats and guinea pigs loaded with stilboesterol were estrogen-dominant, as were the spasmolytic effects of the plant extract on rabbits and guinea pigs. intestinal smooth muscle, appears to be via a non-specific spasmolytic mechanism.
![Fig. 1. Picture of the Hypoxis hemerocallidea corm [Family: Hypoxidaceae]](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10641504.0/18.902.119.652.220.632/fig-1-picture-hypoxis-hemerocallidea-corm-family-hypoxidaceae.webp)
